News release

From: Frontiers

Title: Living with cats does not worsen asthma in children, suggests study

Subtitle: Large-scale study on children with asthma and allergies suggests no link between exposure to cats and asthma severity

Summary: Epidemiologists did a study on more than 30,000 children in Sweden between four and 17 years of age with an existing diagnosis of asthma and allergies. They found that asthma severity and lung function measured over the period 2023 to 2024 did not differ between children in households with at least one cat and children living without cats. There wasn’t any association between the cats’ sex, age, and number per household and asthma outcomes. The authors concluded that exposure to cats does not appear to worsen the outcomes of pediatric asthma, at least in the short term.

Main text: Asthma is the most common chronic disease and one of the main causes of hospitalization among children. The Global Asthma Network has estimated that its global prevalence is 9.1% for children and 11.0% for adolescents, but this percentage varies greatly between countries, regions, and environments. Worldwide, the highest prevalence of pediatric asthma (above 20%) occurs in the British Isles and in parts of Oceania and the Middle East. Known risk factors for developing asthma include exposure to air pollution and smoking, childhood viral infections, obesity, and pre-existing allergies like eczema or hay fever.

Patients anecdotally self-report that exposure to animal dander appears to trigger asthma attacks. However, clinical and epidemiological data on this is so far contradictory, coming mostly from small studies on subgroups that aren’t necessarily representative of the wider population. Now, researchers have demonstrated in Frontiers in Allergy that sharing a home with cats may not worsen the outcomes of children with asthma and allergies.

Large pediatric sample

“Here we show in a nationwide cohort of children in Sweden with asthma and allergies, that children living with a cat had similar asthma severity, exacerbation, asthma control, and lung function to children living without cats in the short term,” said corresponding author Dr Resthie R Putri, a postdoctoral fellow at Karolinska Institutet in Stockholm.

“We also did not see any differences in asthma outcomes related to the number of cats, the cat’s sex, or the cat’s age.”

In 2023, Putri and colleagues began a study on a cohort of 30,277 children – between four and 17 years old at the time – born between 2006 and 2020 and diagnosed with asthma or an airway allergy. They followed these over 24 months until 2024 to track asthma outcomes, drawing records on diagnoses, emergency visits, prescribed medications, and asthma control test and spirometry tests from linked data in the Swedish National Patient Register, Prescribed Drug Register, and National Airway Register.

In Sweden, registration in the National Cat Register has been mandatory since 2023 for all pet cats born after 2008. For each child, the authors noted whether the parental household had at least one cat in 2023, as was true for 9.4% of the children.

Cats don't worsen asthma in kids

The results showed that there was no significant association between exposure to pet cats and asthma outcomes. For example, moderate-to-severe asthma – based on prescribed asthma medications – occurred in 9.6% of the cat-exposed children and 10.1% of the non-exposed children. Asthma ‘exacerbation’ (also known as an attack or flare-up) occurred in 3.3% of the cat-exposed children and 3.5% of the non-exposed children.

Among a subset of 1,428 children for whom asthma control and lung spirometry data were available, 97 (6.8%) lived with cats. There were no significant differences between the two groups in two common measures of lung function.

“One possible explanation is that cat allergen exposure is very common, even outside the home. Children who do not have cats at home may still be exposed in shared environments such as schools or public transportation, which could explain why we didn’t see a difference,” said Putri.

“While these large-scale findings provide valuable insight, we lacked data on which allergens the children were sensitized to, and because the National Cat Register is relatively new, some children living with cats may have been misclassified as unexposed,” she cautioned.

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